[build][asm] Pass ASFLAGS to the assembler instead of CFLAGS

* Add `-Wa,--noexecstack` to both `ASFLAGS` and `CFLAGS`
* Pass `ASFLAGS` to `.S` compilation instead of `CFLAGS`

Fixes #3006.

6 files changed, 16 insertions, 11 deletions

diff --git a/contrib/linux-kernel/test/Makefile b/contrib/linux-kernel/test/Makefile
index dc76a5f4..be82b3fb 100644
--- a/contrib/linux-kernel/test/Makefile
+++ b/contrib/linux-kernel/test/Makefile
@@ -24,7 +24,7 @@ LINUX_ZSTD_OBJECTS0   := $(LINUX_ZSTD_FILES:.c=.o)
 LINUX_ZSTD_OBJECTS    := $(LINUX_ZSTD_OBJECTS0:.S=.o)
 
 %.o: %.S
-	$(CC) -c $(CPPFLAGS) $(CFLAGS) $^ -o $@
+	$(COMPILE.S) $(OUTPUT_OPTION) $<
 
 liblinuxzstd.a: $(LINUX_ZSTD_OBJECTS)
 	$(AR) $(ARFLAGS) $@ $^
diff --git a/lib/Makefile b/lib/Makefile
index 00fc535b..ef202183 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -212,11 +212,11 @@ $(ZSTD_STATLIB_DIR)/%.o : %.c $(ZSTD_STATLIB_DIR)/%.d | $(ZSTD_STATLIB_DIR)
 
 $(ZSTD_DYNLIB_DIR)/%.o : %.S | $(ZSTD_DYNLIB_DIR)
 	@echo AS $@
-	$(COMPILE.c) $(OUTPUT_OPTION) $<
+	$(COMPILE.S) $(OUTPUT_OPTION) $<
 
 $(ZSTD_STATLIB_DIR)/%.o : %.S | $(ZSTD_STATLIB_DIR)
 	@echo AS $@
-	$(COMPILE.c) $(OUTPUT_OPTION) $<
+	$(COMPILE.S) $(OUTPUT_OPTION) $<
 
 MKDIR ?= mkdir
 $(BUILD_DIR) $(ZSTD_DYNLIB_DIR) $(ZSTD_STATLIB_DIR):
diff --git a/lib/libzstd.mk b/lib/libzstd.mk
index 73a8cd5d..6e9a6439 100644
--- a/lib/libzstd.mk
+++ b/lib/libzstd.mk
@@ -95,8 +95,9 @@ DEBUGFLAGS= -Wall -Wextra -Wcast-qual -Wcast-align -Wshadow \
             -Wvla -Wformat=2 -Winit-self -Wfloat-equal -Wwrite-strings \
             -Wredundant-decls -Wmissing-prototypes -Wc++-compat
 CFLAGS   += $(DEBUGFLAGS) $(MOREFLAGS)
+ASFLAGS  += $(DEBUGFLAGS) $(MOREFLAGS) $(CFLAGS)
 LDFLAGS  += $(MOREFLAGS)
-FLAGS     = $(CPPFLAGS) $(CFLAGS) $(LDFLAGS)
+FLAGS     = $(CPPFLAGS) $(CFLAGS) $(ASFLAGS) $(LDFLAGS)
 
 ifndef ALREADY_APPENDED_NOEXECSTACK
 export ALREADY_APPENDED_NOEXECSTACK := 1
@@ -104,10 +105,12 @@ ifeq ($(shell echo "int main(int argc, char* argv[]) { (void)argc; (void)argv; r
 LDFLAGS += -z noexecstack
 endif
 ifeq ($(shell echo | $(CC) $(FLAGS) -Wa,--noexecstack -x assembler -Werror -c - -o $(VOID) 2>$(VOID) && echo 1 || echo 0),1)
-CFLAGS += -Wa,--noexecstack
+CFLAGS  += -Wa,--noexecstack
+# CFLAGS are also added to ASFLAGS
 else ifeq ($(shell echo | $(CC) $(FLAGS) -Qunused-arguments -Wa,--noexecstack -x assembler -Werror -c - -o $(VOID) 2>$(VOID) && echo 1 || echo 0),1)
 # See e.g.: https://github.com/android/ndk/issues/171
-CFLAGS += -Qunused-arguments -Wa,--noexecstack
+CFLAGS  += -Qunused-arguments -Wa,--noexecstack
+# CFLAGS are also added to ASFLAGS
 endif
 endif
 
diff --git a/programs/Makefile b/programs/Makefile
index da848eb6..f77e1b7f 100644
--- a/programs/Makefile
+++ b/programs/Makefile
@@ -320,7 +320,7 @@ $(BUILD_DIR)/%.o : %.c $(BUILD_DIR)/%.d | $(BUILD_DIR)
 
 $(BUILD_DIR)/%.o : %.S | $(BUILD_DIR)
 	@echo AS $@
-	$(COMPILE.c) $(OUTPUT_OPTION) $<
+	$(COMPILE.S) $(OUTPUT_OPTION) $<
 
 MKDIR ?= mkdir
 $(BUILD_DIR): ; $(MKDIR) -p $@
diff --git a/tests/Makefile b/tests/Makefile
index efcbe976..132fa7a0 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -118,7 +118,7 @@ zstdd_%.o : $(ZSTDDIR)/decompress/%.c
 	$(CC) -c $(CPPFLAGS) $(CFLAGS) $< -o $@
 
 zstdd_%.o : $(ZSTDDIR)/decompress/%.S
-	$(CC) -c $(CPPFLAGS) $(CFLAGS) $< -o $@
+	$(CC) -c $(CPPFLAGS) $(ASFLAGS) $< -o $@
 
 zstdmt%.o : CPPFLAGS += $(MULTITHREAD_CPP)
 
@@ -132,7 +132,7 @@ zstdmt_d_%.o : $(ZSTDDIR)/decompress/%.c
 	$(CC) -c $(CPPFLAGS) $(CFLAGS) $< -o $@
 
 zstdmt_d_%.o : $(ZSTDDIR)/decompress/%.S
-	$(CC) -c $(CPPFLAGS) $(CFLAGS) $< -o $@
+	$(CC) -c $(CPPFLAGS) $(ASFLAGS) $< -o $@
 
 fullbench32: CPPFLAGS += -m32
 fullbench fullbench32 : CPPFLAGS += $(MULTITHREAD_CPP) -Wno-deprecated-declarations
diff --git a/tests/fuzz/Makefile b/tests/fuzz/Makefile
index b707bd95..912348c3 100644
--- a/tests/fuzz/Makefile
+++ b/tests/fuzz/Makefile
@@ -12,6 +12,7 @@
 CFLAGS ?= -O3
 CXXFLAGS ?= -O3
 CPPFLAGS ?=
+ASFLAGS ?=
 LDFLAGS ?=
 ARFLAGS ?=
 LIB_FUZZING_ENGINE ?= libregression.a
@@ -43,6 +44,7 @@ FUZZ_EXTRA_FLAGS := -Wall -Wextra -Wcast-qual -Wcast-align -Wshadow \
 	-Wredundant-decls -Wno-deprecated-declarations \
 	-g -fno-omit-frame-pointer
 FUZZ_CFLAGS := $(FUZZ_EXTRA_FLAGS) $(CFLAGS)
+FUZZ_ASFLAGS := $(FUZZ_EXTRA_FLAGS) $(ASFLAGS)
 FUZZ_CXXFLAGS := $(FUZZ_EXTRA_FLAGS) -std=c++11 $(CXXFLAGS)
 FUZZ_LDFLAGS := -pthread $(LDFLAGS)
 FUZZ_ARFLAGS := $(ARFLAGS)
@@ -127,7 +129,7 @@ rt_lib_decompress_%.o: $(ZSTDDIR)/decompress/%.c
 	$(CC) $(FUZZ_CPPFLAGS) $(FUZZ_CFLAGS) $(FUZZ_ROUND_TRIP_FLAGS) $< -c -o $@
 
 rt_lib_decompress_%.o: $(ZSTDDIR)/decompress/%.S
-	$(CC) $(FUZZ_CPPFLAGS) $(FUZZ_CFLAGS) $(FUZZ_ROUND_TRIP_FLAGS) $< -c -o $@
+	$(CC) $(FUZZ_CPPFLAGS) $(FUZZ_ASFLAGS) $(FUZZ_ROUND_TRIP_FLAGS) $< -c -o $@
 
 rt_lib_dictBuilder_%.o: $(ZSTDDIR)/dictBuilder/%.c
 	$(CC) $(FUZZ_CPPFLAGS) $(FUZZ_CFLAGS) $(FUZZ_ROUND_TRIP_FLAGS) $< -c -o $@
@@ -151,7 +153,7 @@ d_lib_decompress_%.o: $(ZSTDDIR)/decompress/%.c
 	$(CC) $(FUZZ_CPPFLAGS) $(FUZZ_CFLAGS) $< -c -o $@
 
 d_lib_decompress_%.o: $(ZSTDDIR)/decompress/%.S
-	$(CC) $(FUZZ_CPPFLAGS) $(FUZZ_CFLAGS) $< -c -o $@
+	$(CC) $(FUZZ_CPPFLAGS) $(FUZZ_ASFLAGS) $< -c -o $@
 
 d_lib_dictBuilder_%.o: $(ZSTDDIR)/dictBuilder/%.c
 	$(CC) $(FUZZ_CPPFLAGS) $(FUZZ_CFLAGS) $< -c -o $@